After you added all existing reservations and the correct price/rates for seasonal periods [see how here], you will be ready to run the first complete Push (Push - full).
Please find this on Channel Manager > Dashboard OTA > inside the OTA you're connecting now.
Make sure your rooms are mapped (selected accordingly with Local rooms), and then you're ready to press 'Run Push (full)'.
After that you can see your profile at Booking.com and check if the changes you made on price were included (in case you did not change the price, you won't see any change)
After that you can just select "enable" for the automatic push and automatic pull.
Finally you can go to Booking.com and create a fake reservation to see if it appears in your calendar. It should appear after some seconds :)